Sex differences have been described for almost all features of schizophrenia (prevalence, incidence, age of onset, clinical presentation, course, response to treatment)16. To assess if the variance in liability tagged by SNPs on autosomes differs between the sexes we undertook a bivariate analysis considering male cases and controls as one trait and female cases and controls as the other trait; the two independent subsets are related through the coefficients of similarity calculated from SNPs (Online Methods equation 2). The correlation in liabilities explained by SNPs between the sexes was very high (0.89 s.e. 0.06, not significantly different from 1) (Table 2) implying that the majority of additive genetic variance is shared between the sexes. We also investigated variance explained by genotyped SNPs on the X chromosome for the ISC and MGS data sets and concluded that the variance explained by the X chromosome is consistent with expectation given its length (Supplementary Table 3).
